Answer to Question #15445 in Inorganic Chemistry for chase

Question

A solution may contain Ag
, Pb and Hg. A white precipitate forms on addition of
6 M HCl. The precipitate is insoluble in hot water. The residue turns black on
addition of ammonia. Which of the ions are present, which are absent, and which
remain undetermined? State your reasoning. Note: On paper unknowns such as this
one, confirmatory tests are usually not included.

Answer 1

PbCl₂ is soluble in hot water so it is absent

Hg₂Cl₂(s) + 2NH₃(aq) --> Hg(s) + HgNH₂Cl(s) + NH₄Cl (aq) (Hg is black precipitate)
AgCl is undetermined